Effect of the Inhibition of Mitochondrial Creatine Kinase Activity on the Clinical Diagnosis of Suspected Acute Myocardial Infarction

Background: Creatine kinase isoenzyme MB (CK-MB) activity using the immunoinhibition method has been measured in clinical laboratories. However, the presence of mitochondrial CK (MtCK) abnormally increases CK-MB activity when measured using the conventional method, which can lead to misdiagnosis of acute myocardial infarction (AMI). A new CK-MB activity assay kit that can inhibit MtCK activity was recently developed; here, we describe the performance of this kit. Methods: The analytical performance of this new kit was investigated using 338 samples, and the correlation between results obtained using the new and conventional kits were analyzed. Results: A good correlation (r > 0.993) was found between results obtained using the new and conventional kits in the sera from patients with obvious AMI (n = 91). However, a poor correlation exists between results obtained using the new and conventional kits in samples from patients without AMI. Electrophoretic CK isoenzyme analysis confirmed that the appearance of MtCK in nearly all samples from patients with malignant tumors makes poor correlation. Conclusion: Inhibiting MtCK activity is important for diagnosing AMI. The new method may provide a more accurate value of CK-MB activity for clinical use.